Selected Abstracts

JOURNAL OF FOOD QUALITY, Issue 4 2010MARÍA G. GOÑI
ABSTRACT
Butterhead lettuce was characterized by physical, microbiological and nutritional quality indices as a function of plant zoning and soil management (bare soil and mulch).
Quality indices were measured in all the rings from the external toward the internal ratio.
Assayed indices were: relative water content, water content, free and bound water, and the ratio between free water and total water, leaf area and color, total microbial counts (TMC) and ascorbic acid content (AA).
The lettuce characterization by rings showed a remarkable plant zoning as a function of leaf age and development; also, some initial indices were affected by the soil management employed.
Plastic mulches affect the microclimate around the plant, resulting in better plant water status.
However, the use of black plastic covers could absorb sunlight therefore increasing soil temperature and causing lower AA and higher TMC in lettuce tissue.
PRACTICAL APPLICATIONS
During lettuce development, each leaf had a different level of exposure to environmental conditions, such as light, humidity, nutrients absorption and temperature affecting the quality indices of the raw material and introducing a source of variability in the physico-chemical, biochemical, nutritional and microbiological indices within the plant.
In this way, the location of the leaf within the whole plant is an important factor to be considered.
Moreover, during lettuce heads trading, it is a common practice to remove the external leaves as storage advances.
These leaves are more perishable than middle and internal ones because of their direct exposure to environmental conditions.
Understanding the way in which physical, microbiological and nutritional indices were distributed in the whole lettuce plant could be of interest, to know the value of the losses of regular green grocers' practices, from a nutritional and a safety point of view.
[source]

USE OF SOIL AND WATER PROTECTION PRACTICES AMONG FARMERS IN THE NORTH CENTRAL REGION OF THE UNITED STATES,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2000Ted L. Napier
ABSTRACT: Data were collected in the fall of 1998 and the winter of 1999 from 1,011 land owner-operators within three watersheds in the North Central Region of the United States to assess adoption of soil and water protection practices.
Farm owner-operators were asked to indicate how frequently they used 18 different agricultural production practices.
Many farmers within the three watersheds had adopted conservation protection practices.
However, they also employed production practices that could negate many of the environmental benefits associated with conservation practices in use.
Comparison of adoption behaviors used in the three watersheds revealed significant differences among the study groups.
Respondents in the Iowa and Ohio watersheds reported greater use of conservation production systems than did farmers in Minnesota.
However, there were no significant differences between Ohio and Iowa farmers in terms of use of conservation production practices.
This was surprising, since farmers in the Ohio watershed had received massive amounts of public and private investments to motivate them to adopt and to continue using conservation production systems.
These findings bring into serious question the use of traditional voluntary conservation programs such as those employed in the Ohio watershed.
Study findings suggest that new policy approaches should be considered.
It is argued that "whole farm planning" should be a significant component of new agricultural conservation policy.
[source]

THE EFFICIENCY OF SEQUESTERING CARBON IN AGRICULTURAL SOILS

CONTEMPORARY ECONOMIC POLICY, Issue 2 2001GR Pautsch
Agricultural tillage practices are important human-induced activities that can alter carbon emissions from agricultural soils and have the potential to contribute significantly to reductions in greenhouse gas emission (Lal et al., The Potential of U.S. Cropland, 1998).
This research investigates the expected costs of sequestering carbon in agricultural soils under different subsidy and market-based policies.
Using detailed National Resources Inventory data, we estimate the probability that farmers adopt conservation tillage practices based on a variety of exogenous characteristics and profit from conventional practices.
These estimates are used with physical models of carbon sequestration to estimate the subsidy costs of achieving increased carbon sequestration with alternative subsidy schemes.
[source]

Evaluation of the SWEEP model during high winds on the Columbia Plateau ,

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 11 2009G. Feng
Abstract
A standalone version of the Wind Erosion Prediction System (WEPS) erosion submodel, the Single-event Wind Erosion Evaluation Program (SWEEP), was released in 2007.
A limited number of studies exist that have evaluated SWEEP in simulating soil loss subject to different tillage systems under high winds.
The objective of this study was to test SWEEP under contrasting tillage systems employed during the summer fallow phase of a winter wheat,summer fallow rotation within eastern Washington.
Soil and PM10 (particulate matter ,10 µm in diameter) loss and soil and crop residue characteristics were measured in adjacent fields managed using conventional and undercutter tillage during summer fallow in 2005 and 2006.
While differences in soil surface conditions resulted in measured differences in soil and PM10 loss between the tillage treatments, SWEEP failed to simulate any difference in soil or PM10 loss between conventional and undercutter tillage.
In fact, the model simulated zero erosion for all high wind events observed over the two years.
The reason for the lack of simulated erosion is complex owing to the number of parameters and interaction of these parameters on erosion processes.
A possible reason might be overestimation of the threshold friction velocity in SWEEP since friction velocity must exceed the threshold to initiate erosion.
Although many input parameters are involved in the estimation of threshold velocity, internal empirical coefficients and equations may affect the simulation.
Calibration methods might be useful in adjusting the internal coefficients and empirical equations.
Additionally, the lack of uncertainty analysis is an important gap in providing reliable output from this model.
Published in 2009 by John Wiley & Sons, Ltd.
[source]

ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 1 2006M. Mathew
Abstract
The efficacy of indigenous microorganisms to degrade diesel oil in contaminated mainland sites in Singapore was investigated.
A semi-scale trial was made by spiking topsoil with 6,% [w/w] of diesel oil.
The results indicated that in the presence of NPK commercial (Rosasol®) fertilizer a 53,% reduction in contaminant concentration was recorded after 60,days compared to untreated controls while the addition of a mixture of urea and K2HPO4 effected a 48,% reduction in the Total Recoverable Petroleum Hydrocarbons.
A commercial culture and an enriched/isolated microbial association proved to be the least effective with 25 and 9,% reductions, respectively.
The results confirmed the bioremediation potential of indigenous microorganisms for diesel-oil contaminated mainland soil.
Identification of the persistent compounds was done and perceived as a tool in decision-making on strategies for speeding up of the degradation process to achieve clean-up standards in shorter remediation periods.
[source]

Widespread capacity to metabolize polychlorinated biphenyls by diverse microbial communities in soils with no significant exposure to PCB contamination

ENVIRONMENTAL MICROBIOLOGY, Issue 8 2007Alexandre J. Macedo
Summary
The purpose of this work was to determine the extent of microbial metabolic potential for polychlorinated biphenyls (PCBs) in soils that have had no previous exposure to this class of xenobiotic pollutants.
Soil and sediment samples of distinct characteristics from six sites in Germany were used to inoculate PCB oil (Aroclor 1242) microdroplets.
All samples yielded multispecies biofilms, as revealed by single-strand conformation polymorphism (SSCP) analyses of polymerase chain reaction (PCR) analysis of 16S rRNA genes, and sequence analysis of the main amplicons.
Microbes representing 20 different operational taxonomic units (OTUs) were identified in the biofilms, but only a few were common to all biofilms, namely those closely related to Aquabacterium sp., Caulobacter sp., Imtechium assamiensis, Nevskia ramosa, Parvibaculum lavamentivorans and Burkholderia sp.
The PCB biofilm communities were always distinct from control biofilms developing from the same samples in the absence of PCB.
All PCB droplet-grown biofilms degraded multiple PCB congeners but differed in the congener spectra they degraded.
These findings reveal that microbial potential to degrade PCBs is widespread in soils that have not been subjected to PCB contamination, and that this potential is characteristic of consortia of very diverse phylogenetic composition.
[source]

Effects of amendments of N, P, Fe on phytoextraction of Cd, Pb, Cu, and Zn in soil of Zhangshi by mustard, cabbage, and sugar beet

Arsenic Binding to Iron(II) Minerals Produced by An Iron(III)-Reducing Aeromonas Strain Isolated from Paddy Soil

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2009Xin-Jun Wang
Abstract
An iron-reducing bacterial strain was isolated from a paddy soil and identified as a member of the Aeromonas group by 16S rRNA gene sequence analysis.
When the cells were growing with dissolved Fe(III) as the electron acceptor in the presence of As(V), Fe(II) minerals (siderite and vivianite) were formed and dissolved.
As was removed efficiently from solution.
When the cells were growing with the Fe(III) hydroxide mineral (ferrihydrite) as the electron acceptor in the presence of As(V), ferrihydrite was reduced and dissolved As(V) concentrations decreased sharply.
The present study results demonstrated first that members of the Aeromonas group can reduce Fe(III) in paddy soils and second that iron reduction does not necessarily lead to arsenic mobilization.
However, As immobilization can occur in environments that contain significant concentrations of counterions such as bicarbonate and phosphate.
[source]

Influence of hydroxypropyl-,-cyclodextrin on the extraction and biodegradation of phenanthrene in soil

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2004Brian J. Reid
Abstract
A study was conducted to investigate the effect of hydroxypropyl-,-cyclodextrin (HPCD) on the aging and biodegradation of phenanthrene (PHE) in soil.
Soil was spiked with PHE at 25 mgPHE/kgSOIL and HPCD at a range of concentrations from 0 to 3.5 gHPCD/kgSOIL and aged for 1, 84, and 322 d. At each time point, a variety of analyses were performed to assess the loss and aging of the PHE in the soil.
Methods included determination of total PHE remaining, dichloromethane (DCM) and butan-1-ol (BuOH) extractions, and determination of PHE extractable by an aqueous HPCD shake extraction.
Mineralization assays were also carried out to assess the availability of the PHE to a PHE-degrading bacterial inoculum.
It was found that the presence of HPCD in the soils increased PHE loss from the aged soil systems, particularly at the higher application rates.
Dichloromethane and BuOH extractabilities were reduced with aging and increasing HPCD concentration, as was the amount of PHE that was extractable using an aqueous HPCD shake extraction or that was available for mineralization.
The DCM and BuOH extraction yielded similar results, and both greatly overestimated the availability of the PHE to the degraders, whereas the HPCD extraction results were very similar to that of PHE biodegradation.
This study indicates that cyclodextrins have potential for use as alternatives to surfactants in enhancing the desorption/solubilization and degradation of recalcitrant organic contaminants in soil.
[source]

Bauxite manufacturing residues from Gardanne (France) and Portovesme (Italy) exert different patterns of pollution and toxicity to sea urchin embryos

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2002Giovanni Pagano
Abstract
This study was designed to investigate the composition and toxicity of solid residues from bauxite manufacturing plants.
Soil and dust samples were collected in the proximity of two bauxite plants (Gardanne, France, and Portovesme, Italy).
Samples were analyzed for their content of some selected inorganic contaminants by means of inductively coupled plasma optical emission spectroscopy (ICP-OES) either following acid digestion procedures or by seawater release of soluble components.
Toxicity was tested by sea urchin bioassays to evaluate a set of toxicity endpoints including acute embryotoxicity, developmental defects, changes in sperm fertilization success, transmissible damage from sperm to the offspring, and cytogenetic abnormalities.
Inorganic analysis showed two distinct sets of inorganic contaminants in Gardanne versus Portovesme, including Al, Cr, Cu, Fe, Mn, Pb, Ti, and Zn; sample composition (seawater-soluble cotaminants) and toxicity showed a noteworthy association.
The most severe toxicity to embryogenesis and to sperm fertilization success was exerted by some Portovesme samples (0.03,0.5% w/v), with a significant association between toxicity and dose-related seawater release of Zn, Pb, and Mn.
Seawater extraction of a toxic dust sample (G20) from the Gardanne factory showed increasing seawater release of Al, Fe, and Mn; the G20 sample, at the level of 0.5%, affected both developing sea urchin embryos and sperm (offspring quality).
Soil samples around the Gardanne factory showed the highest frequency of toxic soil sites eastward from the factory.
The present data point to solid deposition from bauxite plants as a potential subject of environmental health concern.
The results suggest that extraction methods for evaluating the toxicity of complex mixtures should be based on the environmental availability of mixture components.
The differences in sample toxicity among the tested sites, however, suggest possible site-to-site variability in geochemical and/or technological parameters.
[source]

Pyrene and chrysene fate in surface soil and sand microcosms

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2001J. Chadwick Roper
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are major components of wastes from municipal gas plants and many wood preservatives.
Soil contaminated with these wastes is a potential threat to human health because of the carcinogenicity of many PAHs.
This study follows the fate of two four-ring PAHs, pyrene and chrysene, in three matrices: an adapted soil (obtained from a site contaminated with PAHs for more than 75 years), an uncontaminated soil (with and without an inoculum of adapted soil), and sand mixed with an inoculum of adapted soil.
Radiolabeled pyrene, chrysene, and salicylic acid (a metabolite of PAH biodegradation) were used to trace the mineralization, transformation, extractability, and formation of an unextractable residual over time.
Linear approximations of the rates of these processes were made.
High-performance liquid chromatography (HPLC) analysis of extracts from inoculated soil showed the transient formation of two known metabolites: 1-hydroxypyrene (from pyrene) and 1-hydroxy-2-naphthoic acid (from chrysene).
The amount of extractable label diminished steadily over the course of the study in systems that were not inhibited with sodium azide, whereas the amount of extractable label remained relatively constant in inhibited systems.
Correspondingly, the amount of nonextractable residual label generally increased during each incubation in uninhibited systems, whereas the amount of this residual label remained relatively constant in inhibited systems.
In contrast, the rate and extent of mineralization varied widely across matrix types.
This suggests that alterations of the PAH that impact extractability and residual formation are common, in contrast to mineralization, which was apparently limited to adapted communities.
[source]

Soil and plant diet exposure routes and toxicokinetics of lindane in a terrestrial isopod

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2000José Paulo Sousa
Abstract
In most studies dealing with effects of toxic substances in saprotrophic isopods, animals are exposed to the test substance through contaminated food.
Because these animals can be in a close contact with the soil surface, the substrate, as an exposure pathway, should not be neglected.
Here the authors analyze the toxicokinetic behavior of lindane (,-hexachlorocyclohexane [,-HCH]) in the isopod species Porcellionides pruinosus, comparing two exposure routes: food and two soil types (artificial Organisation for Economic Cooperation and Development [OECD] soil and a natural agricultural soil).
In the feeding experiment, a strong decrease of ,-HCH concentration over time was observed on the food material, with the animals showing a broader range in chemical assimilation efficiency values (averaging 17.7% and ranging from 10 to 40%).
The ,-HCH bioaccumulation results indicate that when animals incubated under both soil types reached a steady state, they displayed much higher body burdens (1,359.60 pg/animal on OECD soil and 1,085.30 pg/animal on natural soil) than those exposed to contaminated food (43.75 pg/animal).
Kinetic models also revealed much lower assimilation and elimination rates in the food experiment (20.66 pg/d and 0.10 pg/d) than in both soil experiments (238.60 pg/d and 350.54 pg/d for the assimilation rate and 0.19 pg/d and 0.32 pg/d for the elimination rate).
Differences in results between exposure routes are discussed according to equilibrium-partitioning theory and the enhanced relevance of the substrate exposure route is analyzed under future prospects on chemical toxicity testing using isopods.
[source]

Soil metaproteomics: a review of an emerging environmental science.

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 6 2009Significance, methodology, perspectives
Summary
Soil is a dynamic system in which microorganisms perform important tasks in organic matter transformations and nutrient cycles.
Recently, some studies have started to focus on soil metaproteomics as a tool for understanding the function and the role of members of the microbial community.
The aim of our work was to provide a review of soil proteomics by looking at the methodologies used in order to illustrate the challenges and gaps in this field, and to provide a broad perspective about the use and meaning of soil metaproteomics.
The development of soil metaproteomics is influenced strongly by the extraction methods.
Several methods are available but only a few provide an identification of soil proteins, while others extract proteins and are able to separate them by electrophoresis but do not provide an identification.
The extraction of humic compounds together with proteins interferes with the latter's separation and identification, although some methods can avoid these chemical interferences.
Nevertheless, the major problems regarding protein identification reside in the fact that soil is a poor source of proteins and that there is not enough sequence-database information for the identification of proteins by mass spectrometric analysis.
Once these pitfalls have been solved, the identification of soil proteins may provide information about the biogeochemical potential of soils and pollutant degradation and act as an indicator of soil quality, identifying which proteins and microorganisms are affected by a degradation process.
The development of soil metaproteomics opens the way to proteomic studies in other complex substrates, such as organic wastes.
These studies can be a source of knowledge about the possibility of driven soil restoration in polluted and degraded areas with low organic matter content and even for the identification of enzymes and proteins with a potential biotechnological value.
[source]

Size and phenotypic structure of microbial communities within soil profiles in relation to different playing areas on a UK golf course

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 5 2008M. D. Bartlett
Summary
Amenity turf accounts for up to 4% of land-use in urban areas, providing key refuges for both above- and below-ground biodiversity.
Golf courses occupy the largest surface area of all sports facilities; however, only a limited amount of microbial ecology has been carried out to investigate differences in the size and structure of microbial communities of the soil.
The soil microbial community is a key agent in nutrient cycling and delivery of other ecosystem goods and services; however, there has been little work focused on amenity turf ecosystems in the UK.
A study of soil microbial community size and structure, on the range of playing areas maintained for the game of golf at a single golf course in relation to depth through the soil profile, was carried out.
Soil from different playing areas showed significant differences in the size (measured using chloroform fumigation extraction) of the microbial community (P < 0.01), with a greater concentration of microbial biomass at 0,75 mm from the surface, compared with deeper zones (P < 0.01).
Principal component analysis of phospholipid fatty acid (PLFA) biomarkers indicated that the community structure was significantly different at 0,75 mm from the surface on all areas of the golf course investigated (P < 0.05, in all cases).
The PLFA biomarkers consistently associated with such discrimination were 16:0 and 18:1,9 c. These findings suggest that there is a consistently larger and similarly structured microbial community associated with the surface thatch layer, commonly found in amenity turf.
[source]

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2008B. Schäffer
Summary
Compaction is a major cause of soil degradation.
It affects not only the porosity of the soil, but also the soil's hydrostructural stability.
Soil that is restored after temporary removal is particularly sensitive to compaction.
We investigated the effects of trafficking with a heavy combine harvester on the shrinkage behaviour of a restored soil that had been gently cultivated for several years.
We tested the hypothesis that compaction decreases the hydrostructural stability of restored soil by analysing simultaneously measured shrinkage and water retention curves of undisturbed soil samples.
Shrinkage strongly depended on clay and organic carbon content.
Taking account of this influence and normalizing the shrinkage parameters with respect to these soil properties, we found pronounced effects of trafficking on shrinkage.
Ten passes with the combine harvester decreased the structural porosity by about 40% at maximum swelling and by about 30% at the shrinkage limit and increased the bulk density by 8% at maximum swelling and by 10% at the shrinkage limit, but did not significantly affect the porosity of the soil plasma.
Moreover, trafficking modified shrinkage, increasing the slopes of the shrinkage curve in the basic and structural shrinkage domains by about 30% and more than 150% after 10 passes, respectively.
Evidently the aggregate structure was strongly destabilized.
The results indicate that the hydrostructural stability of the soil was still very sensitive to compaction by trafficking even 5 years after restoration.
The analysis of shrinkage seemed well suited for the assessment of compaction effects on soil structure.
[source]

Preferential flow and transport in soil: progress and prognosis

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2008B. E. Clothier
Summary
Soil is the first filter of the world's water; its buffering and filtering determine the quality and quantity of our reserves of subterranean and surface water.
Preferential flow can either enhance, or curtail, the capacity of the soil to buffer and filter, and it can compromise, or boost, other ecosystem services.
We ask ,when do preferential flow and transport matter?' We identify 12 of 17 ecosystem services that benefit from preferential flow and three that are affected detrimentally.
We estimate by simple arithmetic the value of preferential flow to ecosystem services to be globally some US$304 billion (109) per year.
We review the 1989 Monte Verità meeting on preferential flow processes and summarize the 2006 presentations, some of which are published in this issue of the Journal.
New technologies and innovative experiments have increased our understanding of the conditions that initiate and sustain preferential flows.
We identify contemporary exigencies, and suggest avenues for their resolution.
We are progressing through observation-led discovery.
Our prognosis is that new data will enable us to develop better models, and more aptly to parameterize existing models, and thereby predict the impact, benefits and detriments of preferential flow in soil.
[source]

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 6 2007M. Kaiser
Summary
Long-term effects of crop rotation and fertilization are mostly observed with respect to the amount of soil organic matter (SOM) and measured in terms of soil organic carbon (SOC).
In this paper, we analyze the SOM composition of samples from long-term agricultural field experiments at sandy and clayey sites that include complex crop rotations and farm-yard manure applications.
The organic matter (OM) composition of the soil samples, OM(Soil), and that of sequentially extracted water, OM(W), and sodium pyrophosphate, OM(PY), soluble fractions was analyzed using Fourier Transform Infrared Spectroscopy (FTIR).
The fraction OM(PY) represented between 13 and 34% of SOC, about 10 times that of OM(W).
Site specific differences in OM(Soil) composition were larger than those between crop rotations and fertilizer applications.
The smaller C=O group content in FTIR spectra of OM(W) compared with OM(PY) suggests that analysis of the more stable OM(PY) fraction is preferable over OM(W) or OM(Soil) for identifying long-term effects, the OM(Soil) and OM(W) fractions and the content of CH groups being less indicative.
Farm-yard manure application leads to a more similar content of C=O groups in OM(PY) between crop rotations and fertilizer plots at both sites.
Short-term effects from soil tillage or potato harvesting on composition of OM require further studies.
[source]

Composition of organic matter in a subtropical Acrisol as influenced by land use, cropping and N fertilization, assessed by CPMAS 13C NMR spectroscopy

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 6 2005J. Dieckow
Summary
We know much about the influence of management on stocks of organic matter in subtropical soils, yet little about the influence on the chemical composition.
We therefore studied by CPMAS 13C NMR spectroscopy the composition of the above-ground plant tissue, of the organic matter of the whole soil and of silt- and clay-size fractions of the topsoil and subsoil of a subtropical Acrisol under grass and arable crops.
Soil samples were collected from three no-till cropping systems (bare soil; oats,maize; pigeon pea + maize), each receiving 0 and 180 kg N ha,1 year,1, in a long-term field experiment.
Soil under the original native grass was also sampled.
The kind of arable crops and grass affected the composition of the particulate organic matter.
There were no differences in the composition of the organic matter in silt- and clay-size fractions, or of the whole soil, among the arable systems.
Changes were observed between land use: the soil of the grassland had larger alkyl and smaller aromatic C contents than did the arable soil.
The small size fractions contain microbial products, and we think that the compositional difference in silt- and clay-size fractions between grassland and the arable land was induced by changes in the soil's microbial community and therefore in the quality of its biochemical products.
The application of N did not affect the composition of the above-ground plant tissue nor of the particulate organic matter and silt-size fractions, but it did increase the alkyl C content in the clay-size fraction.
In the subsoil, the silt-size fraction of all treatments contained large contents of aromatic C. Microscopic investigation confirmed that this derived from particles of charred material.
The composition of organic matter in this soil is affected by land use, but not by variations in the arable crops grown.
[source]

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2002P. Jouquet
Summary
Termites of the subfamily Macrotermitinae play an important role in tropical ecosystems: they modify the soil's physical properties and thereby make food available for other organisms.
Clay is important in the architecture of Macrotermitinae termite nests, and it has been postulated that termites could modify the mineralogical properties of some clays.
We have tested this hypothesis of clay transformation by termites in the laboratory under controlled conditions, using Odontotermes nr. pauperans termite species, one of the main fungus-growing species at Lamto Research Station (Côte d'Ivoire).
Soil handled by termites in nest building was saturated with SrCl2, glycol or KCl and afterwards heated at 250°C for X-ray diffraction analyses.
Termite handling led to an increase in the expandable layers of the component clay minerals.
Heating and saturation by potassium of modified clays did not close the newly formed expandable clay layers.
However, differences occurred between parts of the constructions built by termites, and the clays can be ranked according to their degree of alteration in the following order: unhandled soils < galleries < chamber walls.
Consequently, termites can be seen as weathering agents of clay minerals, as previously shown for micro-organisms and plants.
[source]

Environmental Soil and Water Chemistry: Principles and Applications.

A multi-trait test of the leaf-height-seed plant strategy scheme with 133 species from a pine forest flora

FUNCTIONAL ECOLOGY, Issue 3 2010Daniel C. Laughlin
Summary
1.,Westoby's [Plant and Soil (1998), 199, 213] Leaf-Height-Seed (LHS) plant strategy scheme quantifies the strategy of a plant based on its location in a three-dimensional space defined by three functional traits: specific leaf area (SLA), height, and seed mass.
This scheme is based on aboveground traits and may neglect strategies of belowground resource capture if root functioning is not mirrored in any of the axes.
How then do fine roots fit into the LHS scheme?
2.,We measured 10 functional traits on 133 plant species in a ponderosa pine forest in northern Arizona, USA.
This data set was used to evaluate how well the LHS scheme accounts for the variation in above and belowground traits.
3.,The three most important plant strategies were composed of multiple correlated traits, but SLA, seed mass, and height loaded on separate principle components.
The first axis reflected the widely observed ,leaf economics spectrum'.
Species at the high end of this spectrum had high SLA, high leaf and fine root nitrogen (N) concentration, and low leaf dry matter content.
The second axis reflected variation in seed mass and fine root morphology.
Plants at the positive end of this spectrum were plants with large seeds and low specific root length (SRL).
The third axis reflected variation in height and phenology.
Plants at the positive end of this spectrum were tall species that flower late in the growing season.
4.,Leaf N concentration was positively correlated with fine root N concentration.
SRL was weakly positively correlated with SLA.
SRL was not correlated with fine root N concentration.
Leaf litter decomposition rate was positively correlated with the leaf economics spectrum and was negatively correlated with the height and phenology spectrum.
5.,Leaf traits, seed mass, and height appear to be integrating properties of species that reflect much of the variation in plant function, including root function.
Fine root N concentration was positively mirrored by the leaf economics spectrum, and SRL was inversely mirrored by seed mass.
The leaf and height axes play a role in controlling leaf litter decomposability, indicating that these strategy axes have important consequences for ecosystem functioning.
[source]

Soil and atmospheric water deficits and the distribution of New Zealand's indigenous tree species

FUNCTIONAL ECOLOGY, Issue 2 2001Leathwick J. R.
Summary
1.,An extensive data set describing the composition of New Zealand's remaining indigenous forests was used to estimate the degree of correlation between measures of both soil and atmospheric water deficit and the distribution of common tree species.
2.,For most species, regression models incorporating measures of air saturation deficit in early autumn, as well as an annual integral of root zone water deficit, provided the best explanation of spatial distribution.
This accords strongly with the mechanistic effects of air saturation deficits on transpiration from trees, and the hydraulic risks experienced by trees under high evaporative demand.
3.,Adjustment of root zone water deficits to account for reductions in rainfall in dry years substantially improved model predictions.
This suggests that extreme climatic events, such as the El Niño phase of the Southern Oscillation, are likely to have strongly influenced the historic composition of forests in New Zealand's drier eastern lowlands.
[source]

Geoarchaeology of the Kostenki,Borshchevo sites, Don River Valley, Russia

A Geostatistical Analysis of Soil, Vegetation, and Image Data Characterizing Land Surface Variation

GEOGRAPHICAL ANALYSIS, Issue 2 2007Sarah E. Rodgers
The elucidation of spatial variation in the landscape can indicate potential wildlife habitats or breeding sites for vectors, such as ticks or mosquitoes, which cause a range of diseases.
Information from remotely sensed data could aid the delineation of vegetation distribution on the ground in areas where local knowledge is limited.
The data from digital images are often difficult to interpret because of pixel-to-pixel variation, that is, noise, and complex variation at more than one spatial scale.
Landsat Thematic Mapper Plus (ETM+) and Satellite Pour l'Observation de La Terre (SPOT) image data were analyzed for an area close to Douna in Mali, West Africa.
The variograms of the normalized difference vegetation index (NDVI) from both types of image data were nested.
The parameters of the nested variogram function from the Landsat ETM+ data were used to design the sampling for a ground survey of soil and vegetation data.
Variograms of the soil and vegetation data showed that their variation was anisotropic and their scales of variation were similar to those of NDVI from the SPOT data.
The short- and long-range components of variation in the SPOT data were filtered out separately by factorial kriging.
The map of the short-range component appears to represent the patterns of vegetation and associated shallow slopes and drainage channels of the tiger bush system.
The map of the long-range component also appeared to relate to broader patterns in the tiger bush and to gentle undulations in the topography.
The results suggest that the types of image data analyzed in this study could be used to identify areas with more moisture in semiarid regions that could support wildlife and also be potential vector breeding sites.
[source]

Soil,atmosphere exchange of CH4, CO, N2O and NOx and the effects of land-use change in the semiarid Mallee system in Southeastern Australia

GLOBAL CHANGE BIOLOGY, Issue 9 2010IAN GALBALLY
Abstract
The semiarid and arid zones cover a quarter of the global land area and support one-fifth of the world's human population.
A significant fraction of the global soil,atmosphere exchange for climatically active gases occurs in semiarid and arid zones yet little is known about these exchanges.
A study was made of the soil,atmosphere exchange of CH4, CO, N2O and NOx in the semiarid Mallee system, in north-western Victoria, Australia, at two sites: one pristine mallee and the other cleared for approximately 65 years for farming (currently wheat).
The mean (± standard error) rates of CH4 exchange were uptakes of ,3.0 ± 0.5 ng(C) m,2 s,1 for the Mallee and ,6.0 ± 0.3 ng(C) m,2 s,1 for the Wheat.
Converting mallee forest to wheat crop increases CH4 uptake significantly.
CH4 emissions were observed in the Mallee in summer and were hypothesized to arise from termite activity.
We find no evidence that in situ growing wheat plants emit CH4, contrary to a recent report.
The average CO emissions of 10.1 ± 1.8 ng(C) m,2 s,1 in the Mallee and 12.6 ± 2.0 ng(C) m,2 s,1 in the Wheat.
The average N2O emissions were 0.5 ± 0.1 ng(N) m,2 s,1 from the pristine Mallee and 1.4 ± 0.3 ng(N) m,2 s,1 from the Wheat.
The experimental results show that the processes controlling these exchanges are different to those in temperate systems and are poorly understood.
[source]

Assessing the effect of elevated carbon dioxide on soil carbon: a comparison of four meta-analyses

GLOBAL CHANGE BIOLOGY, Issue 8 2009BRUCE A. HUNGATE
Abstract
Soil is the largest reservoir of organic carbon (C) in the terrestrial biosphere and soil C has a relatively long mean residence time.
Rising atmospheric carbon dioxide (CO2) concentrations generally increase plant growth and C input to soil, suggesting that soil might help mitigate atmospheric CO2 rise and global warming.
But to what extent mitigation will occur is unclear.
The large size of the soil C pool not only makes it a potential buffer against rising atmospheric CO2, but also makes it difficult to measure changes amid the existing background.
Meta-analysis is one tool that can overcome the limited power of single studies.
Four recent meta-analyses addressed this issue but reached somewhat different conclusions about the effect of elevated CO2 on soil C accumulation, especially regarding the role of nitrogen (N) inputs.
Here, we assess the extent of differences between these conclusions and propose a new analysis of the data.
The four meta-analyses included different studies, derived different effect size estimates from common studies, used different weighting functions and metrics of effect size, and used different approaches to address nonindependence of effect sizes.
Although all factors influenced the mean effect size estimates and subsequent inferences, the approach to independence had the largest influence.
We recommend that meta-analysts critically assess and report choices about effect size metrics and weighting functions, and criteria for study selection and independence.
Such decisions need to be justified carefully because they affect the basis for inference.
Our new analysis, with a combined data set, confirms that the effect of elevated CO2 on net soil C accumulation increases with the addition of N fertilizers.
Although the effect at low N inputs was not significant, statistical power to detect biogeochemically important effect sizes at low N is limited, even with meta-analysis, suggesting the continued need for long-term experiments.
[source]

Effects of soil frost on soil respiration and its radiocarbon signature in a Norway spruce forest soil

GLOBAL CHANGE BIOLOGY, Issue 4 2009JAN MUHR
Abstract
Apart from a general increase of mean annual air temperature, climate models predict a regional increase of the frequency and intensity of soil frost with possibly strong effects on C cycling of soils.
In this study, we induced mild soil frost (up to ,5 °C in a depth of 5 cm below surface) in a Norway spruce forest soil by removing the natural snow cover in the winter of 2005/2006.
Soil frost lasted from January to April 2006 and was detected down to 15 cm depth.
Soil frost effectively reduced soil respiration in the snow removal plots in comparison to undisturbed control plots.
On an annual basis 6.2 t C ha,1 a,1 were emitted in the control plots compared with 5.1 t C ha,1 a,1 in the snow removal plots.
Only 14% of this difference was attributed to reduced soil respiration during the soil frost period itself, whereas 63% of this difference originated from differences during the summer of 2006.
Radiocarbon (,14C) signature of CO2 revealed a considerable reduction of heterotrophic respiration on the snow removal plots, only partly compensated for by a slight increase of rhizosphere respiration.
Similar CO2 concentrations in the uppermost mineral horizons of both treatments indicate that differences between the treatments originated from the organic horizons.
Extremely low water contents between June and October of 2006 may have inhibited the recovery of the heterotrophic organisms from the frost period, thereby enhancing the differences between the control and snow removal plots.
We conclude that soil frost triggered a change in the composition of the microbial community, leading to an increased sensitivity of heterotrophic respiration to summer drought.
A CO2 pulse during thawing, such as described for arable soils several times throughout the literature, with the potential to partly compensate for reduced soil respiration during soil frost, appears to be lacking for this soil.
Our results from this experiment indicate that soil frost reduces C emission from forest soils, whereas mild winters may enhance C losses from forest soils.
[source]